I have given up on my beer gun in favor of the BMBF
because of the same issue you are having. In all honesty though, I think my biggest problem was overcarbonation. (I was an idiot ans let the salesman talk me into a "better" regulator for the same price and now I just have a high pressure reg trying to guestimate the lower pressures.)
Do you have the same problems when filling a glass off the tap? It is easy to over carb when force carbonating. Here is a chart for CO2 volumes
that you should have around. There are more comprehensive guides to getting it right and having a balance system around.